Question 400585 in Javascript Question posted in
A very good W3school tutorial can be found here.

Javascript – type coersion in JS

Is there any practical difference between Number() and + other than performance or intent?

Tried googling, tried searching for posts from other sites and asked AI but couldn’t find any practical or technical answer.
below code is from AI , in all cases the output is always same. Couldnt find any practical difference.

console.log("Unary + Operator vs Number Constructor");

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type here

// Conversion of Numeric Strings
let str1 = "42";
console.log("Unary +: ", +str1);         // Output: 42
console.log("Number: ", Number(str1));   // Output: 42

// Conversion of Non-numeric Strings
let str2 = "abc";
console.log("Unary +: ", +str2);         // Output: NaN
console.log("Number: ", Number(str2));   // Output: NaN

// Handling Empty Strings
let str3 = "";
console.log("Unary +: ", +str3);         // Output: 0
console.log("Number: ", Number(str3));   // Output: 0

// Handling Strings with Whitespace
let str4 = "  ";
console.log("Unary +: ", +str4);         // Output: 0
console.log("Number: ", Number(str4));   // Output: 0

// Handling Boolean Strings
let str5 = "true";
console.log("Unary +: ", +str5);         // Output: NaN
console.log("Number: ", Number(str5));   // Output: NaN

// Handling Special Numeric Strings
console.log("Unary + Infinity: ", +"Infinity");       // Output: Infinity
console.log("Unary -Infinity: ", +"-Infinity");       // Output: -Infinity
console.log("Unary NaN: ", +"NaN");                    // Output: NaN

console.log("Number Infinity: ", Number("Infinity"));  // Output: Infinity
console.log("Number -Infinity: ", Number("-Infinity")); // Output: -Infinity
console.log("Number NaN: ", Number("NaN"));            // Output: NaN

// Conversion of Boolean Values
console.log("Unary + true: ", +true);  // Output: 1
console.log("Unary + false: ", +false); // Output: 0

console.log("Number true: ", Number(true));  // Output: 1
console.log("Number false: ", Number(false)); // Output: 0

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2

Answers


  1. 0

    The performance difference is generally negligible, but in performance-critical applications, the unary + operator might be slightly faster because it is less verbose and involves less function call overhead.

    There are a few similarities in both approaches,

    Both will convert string numerical to numbers & non-numerical will return NaN

    let str = "42";
console.log(+str);        // 42
console.log(Number(str)); // 42

let str = "abc";
console.log(+str);        // NaN
console.log(Number(str)); // NaN

    The same goes for empty strings and boolean values. an empty string will return a 0 and a boolean will return 0 or 1. Difference comes in the objects and symbols

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  2. 0

    There is a slight difference between these two conversion methods-

    1. Number constructor is explicit and readable while unary operator is prone to create defects in code.

    2. Number() constructor has better error handling e.g. –

    In case of Big int

    console.log(Number(20n)) // Output 20
console.log(+20n) // Uncaught error : TypeError: Cannot convert a BigInt value to a number

    Apart from above point I couldn’t find any major differences.

    I hope, it will answer your question !

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